As we have seen, even normal skin needs protection from the effects of simply living. Aging, the sun, the general environment, all take their toll. Acquiring the habit of moisturizing the skin, particularly with a product that contains a sun protection ingredient, is perhaps the most useful thing to be learnt in cosmetic care.

If the skin is to remain smooth and supple, it needs to maintain an adequate moisture level. It is constantly losing its natural moisture, however, through the epidermis by TEWL. This water loss is aggravated by:

exposure to the elements - sun, wind, cold

excessive use of degreasing products on the skin

central heating and air conditioning

sebum flow slowing down with age.

What is the best facial moisturizer?

The best facial moisturizer is a product that hydrates the skin, and/or protects the skin from dehydration. That is, it is designed to improve water retention in the epidermis, particularly in the stratum corneum.

Moisturizers are primarily intended to help the skin to function properly in conditions of cold and wind. They are usually creams, lotions or serums of a consistency that varies from light to heavy depending on their content of thickening agents. These creams are essentially oil-in-water emulsions, consisting of tiny droplets of oil held in a watery base, rather like salad dressings: in these emulsions the watery part is called the continuous phase. Salad dressings, however, separate rapidly into their watery and oily constituents; moisturizers, on the other hand, must not separate out even during long-term storage. So part of the skill for a specialist in the formulation of the best facial moisturizer lies in the ability to create a formula that can hold the oil in the water base for a long time without separation or deterioration. This is done by the incorporation of approved and safe stabilisingingredients.

An alternative type of moisturizer is a water-in-oil emulsion, in which the oily part forms the continuous phase. These tend to be heavier and more greasy, and are aesthetically more suitable for use on the dry skin of the hands, as more of the product remains on the skin and minimises the loss of barrier lipids on subsequent washing or sweating. Skilful formulators can produce water-in-oil (w/o) emulsions with a high proportion of water. Most people find them pleasanter to use than greasier products.

Modern oil-in-water emulsions can be considered for use on dry skin, particularly on the face, where the greasy nature of water-in-oil products may be found unpleasant. Oil-in-water emulsions penetrate well into the skin and can have a cooling effect.

This bottle originally contained an oil-in-water (o/w) emulsion, but the important oily ingredients have separated out from the watery part. Part of the skill of the cosmetic manufacturer lies in producing a stable product that can last for many months.

Most moisturizers contain substances called humectants. These are substances that are capable of attracting water, and which so help to conserve the water in the skin. One of the oldest and best examples is glycerine, also called glycerol. This has been the standard humectant for many decades and is regarded as completely safe.

Because most cosmetic moisturising products have a water base they must contain preservatives, in order to protect them from being contaminated by bacteria, moulds and yeasts. These micro-organisms are everywhere, in the environment as well as on and in our bodies. Without preservatives, micro-organisms would rapidly spoil the product, and even cause it to become a health hazard. Well-formulated products are likely to contain preservatives, although only tiny amounts are required. The preservatives used are all well known and their concentrations carefully controlled. Parabens are common examples.

Emulsions: (above) the two types of emulsion; (below) an oil droplet in water, surrounded by a ring of stabiliser molecules that prevent it from coalescing with its neighbors.

Skin care and moisturizers

For instance, a heavy-duty moisturizer for the hands will contain a large proportion of a humectant such as glycerol. Under normal conditions, however, this would be too heavy for use on the face, and a lighter formulation would be more appropriate.

A cosmetic moisturizer designed to encourage skin hydration will be made up from a small percentage of water and humectant, blended with oils and emulsified to form a liquid or cream. Night creams can be water-in-oil emulsions as they contain a high proportion of excellent humectants.

The general rule is that the drier the skin and its environment, the richer should be the moisturizer.

Younger people tend to prefer lighter moisturizing products than older generations. This is because the younger the skin, the greater is its capacity to retain water, and the more sebum it produces.

Specialized Moisturizers

Cosmetic companies are now producing skin care moisturizer products that incorporate substances givingprotection against ultraviolet radiation, as well as other ingredients for hydration and exfoliation. Products with sunscreens are intended for regular daily use, not only for application during heat waves or on beach holidays.

As we saw in Chapter 4, there is a good deal of scientific evidence that the daily use of a moisturizer with sunscreen ingredients can reduce the long-term effects of photodamage.

Increasingly men, as well as women, are recognising the need for regular moisturising and the daily use of sunscreens.

How a Moisturizer May Change the Appearance of the Skin

As we saw earlier (Skin Color), the way in which visible light interacts with skin is fundamental to how we see it and judge its condition.

There are several ways in which cosmetic preparations may improve the appearance of the skin. Application of a simple oil-in-water emulsion containing glycerol will smooth down the squames and produce swelling of the stratum corneum. This mechanism is responsible for the surface-smoothing effect that can be seen and felt within minutes after application of a moisturizer to the skin.

In dry stratum corneum only 13-30% of light is transmitted back directly - i.e. at least 60% is scattered. With increasing hydration the stratum corneum becomes more translucent, until transmission of light can reach almost 100%. The amount of visible light directly reaching and returning from melanin and the dermis through the epidermis is much increased. This is responsible for the apparent enhancement of skin color that is often visible immediately after applying a moisturizer.